Calcium chloride within carbon dioxide absorbents prevents Compound A production from sevoflurane

Calcium chloride (CaCl₂)-containing carbon dioxide (CO₂) absorbers are characterized by their ability to produce almost no pentafluoroisopropenyl fluoromethyl ether (Compound A), a potentially nephrotoxic byproduct of sevoflurane, in vitro. However, the precise role of CaCl₂ in this process remains unclear. We aimed to clarify the role of CaCl₂ in vitro and determine whether CaCl₂-containing CO₂ absorbents produce Compound A during prolonged surgery under low- and minimal-flow sevoflurane anesthesia using Japanese brand Yabashi Lime-f (YL-f). In vitro, a reaction between 1 L of sevoflurane gas (8%) with 5% CO₂ and an absorbent specimen (20 g) with or without water was performed in an artificial closed-circuit system for 15 or 60 min at 45 °C. In vivo, patients scheduled for colorectal resection received 2.0 vol% sevoflurane at fresh gas flows of 2.0, 1.0, or 0.5 L/min (N = 6) with YL-f. Gas samples from the anesthetic circuit were collected 6 h after induction and at the conclusion of surgeries lasting over 7 h. Compound A concentrations were measured using gas chromatography-flame ionization detection. Compound A production was observed in CaCl₂-free absorbents but not in those containing CaCl₂ in vitro. During 60-min reactions, CaCl₂-free YL-f derivatives produced a median 3.5 ppm of Compound A, with higher concentrations (7.1 ppm) observed upon the addition of 3 mL of water. YL-f did not produce Compound A, regardless of the presence of water. Compound A was not detected in in vivo samples. In conclusion, CaCl₂ suppresses Compound A production from sevoflurane, likely by trapping water within the anesthetic circuit.